The present invention relates to an internal combustion engine liner.
More specifically, the present invention relates to a treatment of an internal combustion engine liner or an object of similar geometry, aiming to decrease friction losses. The present invention finds a particularly advantageous application to the automobile field, without this being a limitation.
The use of coatings of DLC (Diamond Like Carbon) type on rings to lower the friction coefficient of most metals is perfectly known by those skilled in the art. Such is, for example, the case for ring, piston, jacket assemblies of an internal combustion engine where the friction may approximately generate from 30 to 40% of the engine losses.
To attempt decreasing the friction coefficient, it has been provided to apply a DLC-type coating to the rings, as for example appears from the teachings of document WO 2011/051008. This solution is however not satisfactory.
It should be reminded, from a kinematic viewpoint, that a ring is submitted to a stronger wear than a liner. Indeed, a point of the ring is in permanent contact with the liner in a return cycle of the piston, while a point of the liner is in contact with the ring for a very short time.
Further, to obtain a satisfactory result, it is necessary to apply a very thick DLC coating, with a thickness generally greater than 10 μm, which is an economical disadvantage and raises significant technical difficulties.
Indeed, the large thickness of the DLC layer generates a significant roughness on the ring, requiring to be corrected after deposition, short of which the wearing of the liner would not be acceptable. It can also be observed that the ring reaches high temperatures which may adversely affect the DLC coating.
As indicated, since the wear is lower in the case of the liner, it has been provided to act at the level of the internal surface of the liner to attempt decreasing the friction.
For this purpose, according to the teachings of the state of the art, the engine liner undergoes a finishing operation comprising creating hollow patterns having the function of keeping lubricant in the considered mechanical contact. Such a finishing operation, known as “honing”, is applied either directly in the liner, or in a thick coating applied inside of said liner. This type of solution for example appears from the teachings of patent EP 0716151which relates to a liner having its inside covered with a thick deposit formed by thermal projection, and then submitted to the honing step, which removes up to 10 μm of deposit thickness.
Document WO 2009106981, which refers to a honing step performed after application of the coating, may also be mentioned.
There thus appears from the state of the art that the solutions used to attempt decreasing the friction at the liner level and limiting jamming risks all require a honing step necessary to create raised areas to keep the lubricant in the considered mechanical contact, for example, between the ring and the liner.
Such solutions require a significant quantity of oil on the liner walls. Part of the power is lost in the film shearing.
The invention aims at overcoming these disadvantages in a simple, sure, efficient, and rational way.
The problem that the invention aims at solving is suppressing the honing inside of the liner to minimize the quantity of oil on the liner wall and decrease the forces lost in the oil film shearing.
It is also aimed at decreasing the ring wear to keep an optimal tightness of the segmentation during the engine lifetime.